Heat retarding device and method of making the same



INVENTOR. 426m? 0 7741755 E. D. 'TILLYER HEAT RETARDING DEVICE AND METHOD OF MAKING THE; SAME Flled Dec 24 1938 Jan. 13, 1942.

ATTORNEY.

Po-tented in. s, 1942 c messes HEAT nn'rsnnnm nsvrcn AND Mn'rnonor v MAKING THE sears Edgar n. Tiiiyer, Southbridge, assignor to American Optical Company,

Sonthbridge,

Mass, a voluntary association of Massachw v setts Application December 24, i938, Serial No. 241,718 4; Claims. (c1. 88-24) This invention relates to improvements in i1- luminating and projection apparatus and has particular reference to improved means and method of forming a heat protectionscreen'for the illms or sl des used with such apparatus,

L One of the principal objects of the inventionis to provide improved means and method of forming'a heat screen of transparent material which will transmit a high percentage of the visible Referring to"the drawing Fig, I is a diagrammatic longitudinal side-sectional view through a projection apparatus showing the device embodying'the invention in opera 5 tive relation with said projection apparatus;

Fig. .11 isa sectional plan view looking down on theoperative mechanism of the apparatus and or the said device embodying the invention;

Fig. III is a side elevation 'of the heat screen rays and reduce or eliminate the transmission 0! embodying the invention; and

the invisible or inira-red rays so as to protect the delicate films or slides used with such appa ratus'and which is so supported and correlated with the apparatus as to be protected against Fig; IV is a view generally similar to Fig. In showings modified form of heat screen.

It iswell known that the powerful 111111211113 .tion required in a projection apparatus generates cracking or breaking which might be brought? intense inIra-red'radiations about by the intense heat'ci the projected light rays.

Another object of the invention is to provide improved means and method of forming and,

- -Many dlflerentdevices have been used for protecting the films or slides used with such apparatus from such heat with a view to pre- '.venting ignition, heat blistering and so forth.

supporting a substantially colorless heat screen. of Most of these prior art devices, although emvitreous composition which will have a high transmission of visible light and which will greatcient as regards the absorption of the invisible or inira-red heat rays, also greatly reduced the iv reduce or eliminate the o1 invisvisible rays and also. changed the. color thereof. 'ible light, particularly throughout the inira-red Ellis change or color and reduction of the visible range, so that the effective portion of said heat rays was an inherent function or most priorart screen will not be continuously exposed to the heat of the projected rays 0! the projection apparetus with which such screen is being used.

heat retarding-vitreous screens and rendered it desirable; so as to make such heat protection de vices practical for use in projecting colored pic- Another object is'to provide means or avoiding, turesnby the use of slides having diflerently heat shock in vitreous screens substantially ,sl jcolored pigm r n. to eliminate it possfiiie from silica andc'ontaining at least 60% of phosf phorus expressed 2.5220: and havlngan. inhasuch large reductions oi the visible rays and a1- terlng of the colors in devices of this characterred absorbing ingredient therein and method of supporting said heat'scieen ineffective operaand yet avoid having saiddevices subjected, to the danger of possible cracking and brealdng tive position'whereby the said heatscreen may which might result from the intense heat or the be rotated to' position diilerent portions thereof in the path. of the projected light rays of a pro- Jection apparatus with which said vitreous screens are being used so as to render the said projected rays intercepted thereby.- The present invention, therefore, is directed particularly to th provision of heat screen meansfwhich has. all

'of the desirable characteristics of the prior art screens more resistant to cracking or breahng v a regards the bs rp ion 01 the infrawhen acted upon by heat of said rays.

Other objects and advantages of the invention should become apparent from the following description taken in connection with the accomred or heat; rays, with the elimination of the undesirable loss in the transmission of and the I change of color of the visible rays and which also possesses characteristics which will protect the p 1 drawing and it will be apparent that 'saidscreen againstbecoming overheated andthe many modifications and departures may be made from the specific features and methods disclosed herein without departing from the spirit of the invention as. expressed in the accompanying claims. I, therefore, do not wish to be limited to the specific details of construcln'on, arrangement of parts and methods shown and described as the preferred forms only have been given by way of illustration.

danger oi becoming cracked or broken'during Referring more particularly to the drawing wherein like characters of reference dte like parts throughout the several views the device embodying the invention, as illustrated in Figs. I and III, comprises an annular transparent vitreous screen i mounted'centrally thereof in a plate-like holder 2 rotatable supported on a shaft 3 in a bearing 5. A ring coil 5 having a shouldered portion 8 is fitted about the outer contour edge of the screen member I and is held thereon by a ring I attached to said annular member byscrews or the like means 8. annular screen i is secured to the plate-like holder 2 by a ring 8, similar to the ring '1 but of smaller diameter, through screws or the like means H). I

The heat screen i is formed of a transparent medium having substantially colorless charac terlstics. which will transmit a high percentage the visible rays and possesses means which will reduce or eliminate the transmission or the invisible or infra-red rays. A screen having these characteristics may be formed of a vitreous composition whose analysis may be expressed as follows: P2Os-52 to 77%; material Irom the group consisting of 08-0, BaO,SrO.--U.1 to 12%; material from the group consisting of K20, No.20, LilO-(Ll to 10% and material from the group consisting of A1203, BeO and mixtures of A120: and BeO- to 20%; FeMPOQzfiHzO-l to or by the use of a vitreous material, for example, whose chemical analysis may be expressed Percent P: 73.40 A120 10.8.9 FeaO: 2.04 MsO 4.74 259.0 3.42 B20: 4.34 Sin-1 0.33 N820 0.38

The material resulting from the above compositiomi is reduced toa desired size and tbiclm s and to the contour shape desired. This may be accomplished by suriacing the opposite sides of the material with a suitable abrasive such as emery, rouge and. so forth for producing. the surface texture desired. The heat screen may be formed to the desired size and shape by cutting and edging the said material by. means and, methods employed in the art of manufacturing lenses.

It is particularly desirable that the vitreous materials used'informing said heat screens be substantially free from silica and that they contain at least 50% of phosphorus expressed as P205 and that they contain an inira-red absorbing ingredient such as iron in the ferrous condition. This produces a vitreous material which will be relatively clear and transparent and which possesses the desirable inIra-red absorbing characteristics.

The screen or lens formed or material whose analysis may be expressed as: P205; material from the group consisting or 0:10, BaO, SrO; material from the group consisting 0! K20, N320, L120; material from the group consisting of AlzOa,BeO andmixturesothlzO: andBeO;

and Fe::(PO4):.8HzO, will be substantialw' color-' less and will have the desired inIra-red abs0rbing characteristics. The screen, therefore, while absorbing the infra-red or heat rays, will have an exceptionally high transmission of the visible rays. Most prior art heat screens of this charactor had from 40 to transmission, while the screen embodying the invention, as formed or the vitreous material described above, will have from to transmission. It. is app ent, therefore, that the change in intensity of the light, as brought about by the heat screen embodying the invention will be much less than that of the prior art heat screens mentioned The.

above and will be substantially unnoticeable to The vitreous materials disclosed herein are resistant to weathering, acids and to discoloring, particularly when acted upon by radiation.

It is to be understood that the coefficient of expansion, of applicant/s vitreous material, may be modified to render the said materials more resistant to heat and heat shock. This may be accomplished by altering the percentages of A1203, BeO and so forth to obtain the results de sired.

Heat screens of the character described may be used with either still pictures or moving pictures such as diagrammatically illustrated in the drawing. In instances wherein said heat screens are used with still pictures the said screens may be operated by a separate source or power, such as by a motor or other means, as may also be done in the case 01 motion pictures, if desired.

Although applicant has diagrammatically illus trated one form of motion picture projector it 'a framing opening l4. therein is also alignedwith' said projected light rays. Thesupport 13 has a spaced member l5 also provided with an opening' I8 simulating. the opening H in alignment with said opening. The said openings M and US are substantially co-axial'with the axes of the projection of the condensing lens system I2. The support 13 is provided with a suitable roller llover which the film. l8 is led downwardly between the spaced support members l3 and I5 and over areceiving roller I9. Thefilm then progresses over a series 01 sprocket enrolled membars 2B, 2|, 22, 23 and 24, etc., from which it is then directed to a suitablepick-up roll not shown. This construction is 01 a conventional type projector. The sprockets and various roll members spaced above are operated in the usual manner through suitable operating means.

The heat screen I, as illustrated in Fig. I, is

' supportedior rotation about an axis 3, preferably substantially parallel with the axis. of projection of the light from the light source. ll, so as to intercept the light rays coming from the light source 2 through the condensing lenses l2 prior to the said rays passing through the traming openings ll and I8 and the film located therebetween. As stated above the heat screen is of an annular form and is supported for rotation about an axis 3 substantially parallelwith the axis of the projected light. The said screen I is continuously rotated during use so that diflerent portions thereof continuously move into and out of intercepting position. This prevents the screen from being excessively heated and also allows heated portions thereof to cool during rotation. The screen is rotatably carried by a bracket 29 pivotally secured to the side of the casing of the projector by means of screws or the like 30. The

outer ring. gear 5 or said screen is operated through a small gear 3i mounted on a shaft rotated in the bearing 32 of another bracket 33 secured to the wall in the casing oi the projector and having a drive gear 35 adjacent the opposed end thereoi. The said drive gear 3-! is connected with a coil as mounted on a man as carrying a shutter 31. The shaft 3$ is operated by bevelled gears 28 and 27 driven by means of a suitable pulley 25. These latter parts are standard equipment or the projector and the said pulley 25 is operated through a belt connectlonwith a suitable motor which drives the operating mechanism of the projector. The said projector also has the usual projection lens system 33 by means of which the light rays of the projector and image formed by the film is projected on a suitable receiving screen. It is to be understood, of course.

that the film is intermittently advanced as is usual in film projectors. in this particular instance, the heat screen I is driven through a gear connection with a portion the standard operating equipment of the projector, but it is to be understood that'the said screen may be rotated by a separate motor through a standard reduction gear, ir'desired; particularly in instances when. it is used with still projectors.

Although applicant has shown a screen intergeared with one particular partoi the operating part of the mechanism it is to be understood that it may be inter-geared with any desirable part of the projector. The device may be in the form of a separate attachment made Ior ready application to any projector or may be formed as an integral part thereof.

It is also to be understood that instead of forming the screen from a single piece of vitreous material, as illustrated in Fig. III, the said screen, as shown in Fig. IV, may be formed of a plurality 01' segments 38 joined in edge to edge relation with each other, as illustrated at 40, in a suitable frame support 4! simulating the construction of the screen support means illustrated in Fig. III. 7

The screens embodying the invention have been shown and described as being continuously rotated. It.is to be understood that they may be interconnected with the intermittently operating portion with the mechanism of the projector so that, in instances wherein a screen such as illus trated in Fig. IV is used, the segments may be intermittently advanced into position of use.

This intermittent advancing may be also applied to a heat screen, such as illustrated in Fig. 111, if desired. 'It is to be understood, therefore, that the heat screens may be continuously or intermittently advanced.

The screen illustrated in Fig. IV may also be continuously rotated, if desired. The speed of rotation'would, in all probability, be more rapid than that required for rotation of the screen illustrated in Fig. III.

The construction, illustrated in Fig. IV, enables smaller segments of vitreous material to be used in forming the screen.

When mounting a screen, such as illustrated in Fig. IV, for intermittent movement it is preferably interconnected with the mechanism for intermittently advancing the film and for intermittently exposing and blanking out said film. The screen may be provided with a peripheral gear 32 or may be mounted on a shaft #3 connected with the intermittently operating mechanism of the projector. It'is also to be understood that this screemaswellasthescreeninrimm. may be operated by separate operating mechanism either continuously or intermittently.

Colorless heat screens, as set forth above, are particularly adaptable for use with a projection apparatus utilizing commercially known Kodachrome slldes or films which have difie'rent colored pigments embodied therein and will notalter the color produced by said colored pisments. This is a decided advance in the art of heat screens.

From the foregoing description it will be seen that simple, efficient and economical means and methods have been provided for accomplishing all of the objects and advantages of the invention, particularly that of providing a heat screen having the desirable infra-red or heat absorbing characteristics, exceptionally high transmission of the visible rays and novel means and method of maintaining the temperatureoi said screen below the point 01' cracking'or breaking during use.

Having described my invention, I claim:

1. A heat screen 01 relatively thin sheet-like material for projection apparatus, whose analysis may be expressed as PzOs-52 to 77%; material selected from the group consisting of CaO, BaO, SrO-0.l to 12%; materlalirom the group consisting of mo, NazO, L12O-0.1 to 10% and material from the group consisting of A1303, BeO and mixturesv of AlzQ: and Boo-51:0 20% and Fea(PO4)z.8HzO-1 to 10%, which will permit the transmission of approximately 85 to 90% of the visible rays projected on said material and which will permit the transmission of colored light while maintaining substantially unaltered the true color value of said light.

2. A heat screen oi relatively thin sheet-like material, for projection apparatus. whose analysis may be expressed as Pros-52 to 77%: material selected from the group consisting of CaO, BaO. Bro-01 to 12%; material from the group consisting of K20. NazO, Li:0--0.1 to 10% and material from the group consisting o! Ala-O3, Be!) and mixtures of A120: and Booto 20% and Fe3(PO4) :.8H:O-1 to which, will permit thetransmission of approximately 85 to 90% 01' the,

visible rays projected on said material and which, will permit the transmission of colored light while maintaining substantially unaltered the true color value or said light, said relatively thin sheet-like material being in the form of separate sections supported in relatively intimate edge to edge relation with each other to produce substantially the effect of a continuous screen.

'3. A heat screen of relatively thin sheet-hirematerial for projection apparatus whose analysis may be expressed as Prov-521:0 77%; material'selected from the group consisting 0! Cat). BaO, SrO--0.1 to 12%: material from the group consisting of K10, NazQ, LizO-OJ. to 10% andmaterial from the group consisting of A1203, Be!) and mixtures of A120; and Be0-5 to and FeflPOO 2.3HzO--1 to 10%, which will permit the.

transmission of approximately to or the visible rays projected on said material and which will permit the transmission of colored lightwhile maintaining substantially unaltered the true color value of said light. said relatively thin sheet-like material being in the form of a disclike member comprising a plurality of sections supported in edge to edge relation with each other.

4. A heat screen for use with a dim projector comprising a relatively thin substantially color less light transmitting sheet-like member having the property of selectively absorbing infra-red the chemical characteristics of an aluminumv compound and beryllium compound and mixtures of said aluminum and beryllium compounds and containing a compound of iron in the ferrous condition for infra-red radiation absorption.

5. In a device of the character described the combination of a projection apparatus for projectlng a beam or light and having means tor moving 9. him in said beam of light and a heat screen positioned between said beam of light and said film and in spaced relation with said film, said screen comprising a relatively thin substantially colorless light transmitting sheet-like member having the property of selectively absorbing infra-red radiations, the material of said sheet-like member being substantially free from silica and containing as a major constituent an oxide of phosphorus to the extent or at least 50% with minor quantities of ingredients selected from alkali and alkaline earth groups and stabilized against chemical attack by means of a stabilizer having the chemical characteristics of an aluminum compound and beryllium compound and mix tures of said aluminum and berylliumcompounds and containing a compound of iron in the ferrous condition for infra-red radiation absorption, means rotatably supporting said screen and means interconnecting said screen with said'fllm moving means to impart a rotary movement to said screen when the film is moved.

6. In a device or the character described the combination of a projection apparatus for pro- Jecting a beam of light and having means. for

10 moving a iilm in said beam of light and a heat screen positioned between said beam of light and ,said film and in spaced relation with said film, said screen comprising arelatively thin substantiaily colorless light transmitting sheet-like member having the property of selectively absorbing infra-red radiations, the material of said sheet-like member being substantially free from silica and containing as a major constituent an oxide of phosphorus to the extent of at least50% with minor quantities of ingredients selected from alkali and. alkaline earth groups and stabilized against chemical attack by means oi a stabilizer having the chemical characteristics of an aluminum compound and beryllium compound and mixtures of said aluminum and beryllium compounds and containing a compound or. iron in the ferrous condition for lnfra-red radiation absorption, means. rotatably supporting said screen and means interconnecting said screen with said film moving means, said screen com- 

